1. Field of the Invention
The present invention generally relates to optical head apparatus and, more particularly, to a rotating optical head apparatus for use with an optical recording and/or reproducing apparatus which employs an optical tape as a recording medium.
2. Description of the Related Art
In accordance with the development of technology in which an optical tape is employed as an optical recording medium, an optical recording and/or reproducing apparatus has been proposed, in which an optical head is mounted within a rotating drum and the rotating drum is rotated while the optical tape helically wrapped around the circumferential surface of the rotating drum by a predetermined wrapping angle is being transported, thereby a desired information being optically recorded and reproduced.
This optical recording and/or reproducing apparatus employs the helical scan system, i.e., the system in which a scanning locus of an optical beam emitted from the optical head mounted within the rotating drum is sequentially and obliquely formed with respect to the transport direction of the optical tape, whereby an information can be optical recorded on and reproduced from the scanning locus.
When the optical tape wrapped around the rotating drum is transported and the information is optically recorded and reproduced by the optical head, the optical tape must be transported on the rotating drum stably and smoothly
To this end, such a technique is proposed, in which a layer of air, i.e., so-called air film is formed between the transport surface (circumferential surface) of the rotating drum and the tape surface and the tape is transported under the condition that the tape is floated on the circumferential surface of the rotating drum.
According to the above-mentioned technique, the rotating drum is formed to have a bilayer structure in which an upper drum is formed as a rotating drum having a head and a lower drum is formed as a stationary drum for guiding the tape. Then, the rotating drum is rotated at high speed to supply the air into the spacing between the circumferential surface of the drum and the tape to thereby form the air film. In order to maintain the air film amount (thickness of the air film), such a proposal is also made, in which a spiral groove of pump-out type is formed on one of the opposing surfaces of the rotating drum and the stationary drum and the air is blown out from the spiral groove by the rotation of the rotating drum to thereby increase the air pressure relative to the tape.
However, according to the aforesaid structure, while the tape is in the floated state relative to the rotating drum under the condition that the tape is transported in the stationary state (transported in the forward (FWD) mode) upon recording and reproducing, in the non-stationary state transport (search mode or the like), the tape comes in contact with the rotating drum. There is then the risk that the tape will be damaged.